It is often desired to detect the presence of a liquid over a surface, particularly when the presence of the liquid may indicate an undesired leak that may need attention and repair. A typical example is detecting the presence of water over a floor surface upon which an appliance such as a hot water tank may be located. Typically, hot water tanks are located in out-of-the-way or even hidden places, such as basements, closets and attics, for example, where an undetected water leak may cause substantial water damage to the building that houses the hot water tank. Sump pumps may be employed to actively remove water caused by a leak. Moreover, to prevent potential fire or explosion damage in the example of a gas-heated hot water tank that burns a flammable gas, one may desire to extinguish the burning gas should an undetected water leak drain the water tank.
Many water sensors detect water that rises to a predetermined level in a holding tank, for example. These water sensors typically utilize a float, which activates a switch and an alarm. However, a problem with these types of float sensors is that the sensor typically must be in contact with water during normal operation. Therefore, the sensor is built into or otherwise made a part of the holding tank, sometimes at significant cost. Moreover, these water sensors are not useful in undefined spaces that may not reliably contain the leaking water, such as in a room or attic, or on a platform, table or raised surface, for example.
Other water sensors sound an alarm when a sponge-like material absorbs water and closes an electrical circuit. These water sensors are dependent on electrical power and tend to be unreliable when the electrical power fails or a battery fails that is required to constantly change the cathode and anode that close a circuit when immersed in a pool or puddle of liquid, such as water.
Consequently, a need exists for providing a water sensor that detects the presence of water over a surface, independent of any need for electrical power or a float that must maintain contact with water during operation.